摘要：

This chapter reviews both the genetic properties and the developmental features of homoeotic mutations, and shows why they are rightly considered to be among the most instructive classes of mutations for the genetic study of imaginal disc development. Attention has been given to the various hypotheses that have been proposed to explain homoeotic phenomena, and emphasis has put on these phenomena by the framing of new and interesting theories of genetic regulation and pattern formation. The chapter also discusses the types of homoeotic transformation and the types of homoeotic mutation. The phenomenon of homoeosis is widespread among arthropods and even among many other animals. Genetic mosaics have proved to be a useful tool in the study of cell affinity and cell autonomy in homoerotic structures, of the developmental behavior of small homoeotic patches in normal organs, and of the morphogenesis of homoeotic organs. This method, as well as the study of the phenocritical, the phenocopy-sensitive, and the temperature-sensitive periods, also throw light on the time of homoeotic determination.

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